This invention relates to an image forming apparatus such as a copying machine using a longitudinal photosensitive recording medium, and more particularly to an image forming apparatus in which a photosensitive recording medium after subjected to an exposure process is rewound so as to completely feed back an unexposed portion of the photosensitive recording medium to a predetermined position where the unexposed portion can be subjected to a next exposure process when any abnormality having no influence on the rewinding operation occurs, thereby effectively using the photosensitive recording medium with no vainness.
There has been conventionally known an image forming apparatus using a photosensitive recording medium and a developer (transfer) sheet in which the photosensitive recording medium is exposed to light to form a latent image thereon in an exposure unit, and then superposed over the developer sheet under pressure in a pressure-developing unit to thereby develop the latent image on the photosensitive recording medium into a visible image on the developer sheet.
In this type of the image forming apparatus, a prescribed area (latent image forming area) of the photosensitive recording medium is exposed to light to form a latent image thereon, and then is fed through the pressure-developing unit beyond a separation unit for separating the photosensitive recording medium to the developer sheet. Thereafter, a next exposure process is conducted on a next latent image forming area of the photosensitive recording medium to form another latent image thereon, and then it is fed beyond the separation unit. In this case, an unexposed area (non-latent image forming area) of the photosensitive recording medium which has not been exposed to light in a previous exposure process, is also fed to a position between the exposure unit and the pressure developing unit, beyond the pressure-developing unit, or further beyond the separation unit. That is, the unexposed area (non-latent image forming area) of the photosensitive recording medium in the previous exposure process is not newly used to form a latent image thereon in the next exposure process, and this causes a vain use of the photosensitive recording medium. In order to prevent the photosensitive recording medium from being vainly used in the conventional image forming apparatus, an unexposed area of the photosensitive recording medium which has not been exposed to light in an exposure process and fed between the exposure unit and the pressure developing unit or beyond the separation unit after the exposure process, is fed back (rewound) to the front side of the exposure unit after the pressure-developing process is carried out. Thereafter, the unexposed area of the photosensitive recording medium is subjected to a next or subsequent exposure process to form another latent image thereon.
Further, in the conventional image forming apparatus, if any abnormality for indicating an error of a series of image forming operations such as ah exposure operation, a sheet feeding operation and so on is detected during a rewinding operation of the photosensitive recording medium, all of the image forming operations including the rewinding operations are once ceased, and restored after remedying the abnormality. In this case, a next exposure operation for the photosensitive recording medium is newly commenced for the photosensitive recording medium even though the unexposed area of the photosensitive recording medium is not completely fed back to the predetermined position (that is, even though the unexposed area is not positioned in or in front of the exposure unit (for example, between the exposure unit and the pressure-developing unit)). Therefore, even in the image forming apparatus adopting the rewinding operation of the photosensitive recording medium, a large part of the unexposed area in a previous exposure process is not used for forming a latent image thereon in the next exposure process, and a vain use of the photosensitive recording medium is not completely prevented. As a result, a running cost can not be reduced in this image forming apparatus.
Still further, in this image forming apparatus, if any abnormality is detected during a sheet feeding operation of the developer sheet while superposed over the photosensitive recording medium, all of the operations are once ceased and commenced after the abnormality is remedied. In this case, if the abnormality is one for indicating a lack of the transfer sheet, a break of the lamp (light source) or the like which does not hinder the developer sheet from being fed through the separation unit, only the sheet feeding operation of the developer sheet is not ceased and thus continued until the developer sheet is fed beyond the separation unit. After the developer sheet is fed beyond the separation unit, all of the operations including the sheet feeding operation are ceased. This sheet feeding operation of the developer sheet causes the photosensitive recording medium including an exposed area to be also fed beyond the separation unit together with the developer sheet. As described above, however, a next exposure operation for the photosensitive recording medium is newly commenced even though the unexposed area of the photosensitive recording medium is not completely rewound to the predetermined position. Therefore, immediately after the abnormality is remedied and all of the operations are commenced, a next exposure process is carried out even though the unexposed area of the photosensitive recording medium is not completely rewound to the predetermined position, and thus the unexposed area of the photosensitive recording medium is not used for the next exposure operation. This also causes the photosensitive recording medium to be vainly used.